/Engine/Source/Editor/UnrealEd/Public/SCommonEditorViewportToolbarBase.h
Extension allowing derived classes to add to left-aligned portion of the toolbar slots.
virtual void ExtendLeftAlignedToolbarSlots ( [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SHorizontalBox](API\Runtime\SlateCore\Widgets\SHorizontalBox) > MainBoxPtr, [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SViewportToolBar](API\Editor\UnrealEd\SViewportToolBar) > ParentToolBarPtr ) const